1. Field of the Invention
The present invention pertains to methods and apparatus for injecting fluids to evacuate accumulations of sand and other solids from vertical and, particularly, generally horizontal wellbores.
2. Background
Various devices and systems have been developed for evacuating accumulations of sediment and other solids from oil and gas wells. One improvement in wellbore cleanout equipment and techniques is described and claimed in U.S. Pat. No. 4,671,359 to J. J. Renfro and assigned to the assignee of the present invention. In the system described in the Renfro patent, elongated coilable tubing is inserted into the well through a tubing string and quantities of evacuation fluid are jetted into the wellbore to create sufficient velocity to carry the accumulations of sand and other solids upward through the annulus formed between the outer tubing string and the coilable tube.
However, the increasing development of highly deviated and so called horizontal wellbores has presented certain problems in well cleanout operations in that the direction and velocity of flow of the solids evacuation fluid, using conventional methods and equipment, cannot overcome the forces acting to cause the sand and solids to settle out in the wellbore. Still further, the development of deeper wells has presented certain problems in providing sufficient flow velocity of the solids evacuation fluids without incurring extremely high pumping pressures.
Accordingly, the present invention has been directed to developing improved wellbore cleanout apparatus and methods which are adapted to be used in generally horizontal or highly deviated wellbores, as well as vertical extending wellbores, and which overcome certain problems, including those associated with pumping sufficient quantities of solids evacuation fluids in relatively deep or small diameter wells without incurring fluid flow losses and reduced fluid velocities which are ineffective to perform the required cleaning effect.